L-theanine (L-glutamicacid-γ-monoethylamide) is a unique amino acid found almost exclusively in tea plants (Camellia sinensis).It is the predominant amino acid component in tea,and exists in the free (non-protein) form.A method of microbiological production of L-theanine was developed.Although the complete mechanism of L-theanine action is still under investigation,several studies have been completed showing the various stages of L-theanine metabolism.